What is the ruling on the widespread immodest display among women, and what is the legal evidence for the obligation of the complete, شرعي حجاب (Islamic head covering)?

A woman must cover her 'awrah, and this includes the face and the hands. It is forbidden for her to wear anything that does not conceal the color of her skin, and it is disliked to wear anything that does not conceal the size of her limbs.